Prevention and cure of major diseases of yams
Yam root rot
In the early stage of the onset of root rot of yam, brown irregular spots were formed on the base of vines, and spots expanded to form dark brown long lesions. In the middle of the lesions, the base of the vines shrank and the vines died. The surface of the lesion often has inconspicuous light brown filamentous mildew. The onset of tuber often results in the formation of brown irregular lesions near the terminal buds. If the roots are affected, it can cause root death.
The pathogens of yam root rot can survive in the soil for 2 to 3 years and are transmitted through soil, rain, and fertilisers. It is prone to onset under high temperature and high humidity conditions, with mild onset in drought, heavy onset, and severe onset of flooding in the field.
Control methods: Collect residues and burn out as soon as possible. Implement rotations to avoid continuous production. At the beginning of the disease, 75% chlorothalonil wettable powder 600 times or 50% thiram 500 to 600 times spray is used for prevention and treatment. Spray once every 7~20 days, continuous control 2~3 times.
Yam white rust
Yam white rust mainly damages the leaves. Slightly raised white near-circular to irregular-shaped freckle, the spore mass, appears on the back of the leaf. The surface is slightly lustrous. Some of the leaves have dozens of ecchymosis. The mature skin of the ecchymosis ruptures and a white powdery substance is emitted, namely the pathogenic sporangia. On the front of the leaf, irregular spots with unclear yellow-green borders appear. Sometimes Alternaria spores grow on it and the lesions turn black. The pedicels and flower organs of various strains suffered damage, and the deformity was bent and hypertrophied. The fleshy stems also appeared milky white spots, which became an important feature of this disease. In addition to harming cabbage and radish, the disease also infects cruciferous vegetables such as mustard and root vegetables.
In warm areas, hosts exist throughout the year and germs can be transmitted by sporangia through air currents to complete its anniversary cycle. White rust can germinate at 0 °C ~ 25 °C, incubation period of 7 ~ 10 days. Therefore, the disease mostly occurs in areas with high latitude or high altitude and low temperature years. For example, in Inner Mongolia, Jilin, and Yunnan, the disease has an upward trend. In the case of winter and spring and winter weather in Guangdong Province, the disease is sometimes very serious. In these areas, such as low temperature and rain, the temperature difference between day and night, heavy dew, continuous cropping or partial nitrogen fertilizer, plants too dense, well ventilated and low-lying drainage bad field weight.
Control methods: Annual rotation with non-cruciferous vegetables. After the vegetables are harvested, field residues are removed to reduce the source of bacteria. Early onset of spraying 25% metalaxyl WP 800 times or 58% metalaxyl MnZn WP 500 times, 64% WP 50 times, 50~60 liters per acre spray liquid, Every 10 to 15 days, 1 or 2 times. Http://
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